U.S. patent number 7,612,480 [Application Number 11/954,486] was granted by the patent office on 2009-11-03 for interior permanent magnet motor.
This patent grant is currently assigned to Nidec Corporation. Invention is credited to Yoshio Fujii, Hideaki Suzuki.
United States Patent |
7,612,480 |
Fujii , et al. |
November 3, 2009 |
Interior permanent magnet motor
Abstract
A rotor portion of a motor includes a rotor core and a plurality
of field magnets arranged in a circumferential direction at the
rotor core. The rotor core includes at a flux barrier portion
thereof arranged between a pair of field magnets of opposite
magnetic polarities arranged next to one another a flux barrier
hole. The flux barrier hole is independent of a magnet retaining
hole in which the field magnet is retained. The magnet retaining
hole includes a concave portion extending from a side thereof
nearest to the flux barrier hole toward the corresponding flux
barrier hole.
Inventors: |
Fujii; Yoshio (Kyoto,
JP), Suzuki; Hideaki (Kyoto, JP) |
Assignee: |
Nidec Corporation (Kyoto,
JP)
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Family
ID: |
39497134 |
Appl.
No.: |
11/954,486 |
Filed: |
December 12, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080136281 A1 |
Jun 12, 2008 |
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Foreign Application Priority Data
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Dec 12, 2006 [JP] |
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2006-334201 |
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Current U.S.
Class: |
310/156.53;
310/156.56 |
Current CPC
Class: |
H02K
1/2766 (20130101) |
Current International
Class: |
H02K
21/12 (20060101) |
Field of
Search: |
;310/156.53,156.56,156.57,156.08 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2000-060038 |
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Feb 2000 |
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JP |
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2005-328679 |
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Nov 2005 |
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JP |
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Primary Examiner: Zarroli; Michael C
Attorney, Agent or Firm: Keating & Bennett, LLP
Claims
What is claimed is:
1. A motor comprising: a rotor portion rotating about a central
axis and including: a shaft arranged concentrically with the
central axis; a rotor core having a substantially cylindrical shape
attached to the shaft; and a plurality of field magnets arranged at
an outer circumferential surface of the rotor core facing the
central axis, and each of the plurality of field magnets extending
in a direction that is substantially parallel to the central axis;
wherein the rotor core includes: a plurality of magnet retaining
holes accommodating therein the plurality of field magnets; and a
plurality of flux barrier holes arranged in the direction that is
substantially parallel to the central axis at a space between a
corresponding pair of the plurality of field magnets, one magnet in
the corresponding pair of the plurality of field magnets having a
magnetic polarity different from another magnet in the
corresponding pair of the plurality of field magnets; wherein each
of the plurality of flux barrier holes is independent of a
corresponding pair of the plurality of magnet retaining holes; each
of the plurality of magnet retaining holes includes a concave
portion extending toward a corresponding flux barrier hole; and
each of the plurality of magnet retaining holes includes at a side
thereof facing the corresponding flux barrier hole a pair of side
portions spaced apart from one another, and each of the plurality
of magnet retaining holes includes the concave portion at a portion
radially between the pair of side portions.
2. The motor according to claim 1, wherein a shortest distance
between each of the corresponding pair of the plurality of magnet
retaining holes and the corresponding flux barrier hole arranged
therebetween are equal to one another.
3. The motor according to claim 2, wherein the shortest distance
between each of the corresponding pair of the plurality of magnet
retaining holes and the corresponding flux barrier hole arranged
therebetween and a shortest distance between the corresponding flux
barrier hole and an edge of the rotor core are equal.
4. The motor according to claim 1, wherein the corresponding flux
barrier hole includes a side substantially parallel with an outer
circumferential edge of the rotor core, and a pair of sides each
being substantially parallel with a side of each of the
corresponding pair of the plurality of magnet retaining hole facing
thereto.
5. The motor according to claim 3, wherein the corresponding flux
barrier hole has a substantially triangular shape.
6. The motor according to claim 5, wherein the concave portion
includes an extended concave portion extending in a direction
connecting the corresponding pair of the plurality of field magnets
and arranged adjacent to the corresponding flux barrier hole.
7. The motor according to claim 5, wherein the concave portion
includes a surface that is substantially parallel with a side of
the corresponding flux barrier hole.
8. The motor according to claim 1, wherein a magnetic pole is
defined by a pair of the plurality of field magnets between flux
barrier holes arranged circumferentially next to one another.
9. The motor according to claim 8, wherein the pair of the
plurality of field magnets collectively defining a magnetic pole
are spaced apart from one another in a circumferential
direction.
10. The motor according to claim 3, wherein the corresponding flux
barrier hole has a uniform shape in an axial direction.
11. The motor according to claim 1, wherein the rotor portion
includes at the corresponding flux barrier hole a reinforcement
portion having a lower magnetic permeability than that of the rotor
core.
12. The motor according to claim 11, wherein the rotor portion
includes a rotor cover of non-magnetic substance arranged at both
axial end surfaces of the rotor core covering the plurality of
field magnets, a portion of the rotor cover is filled in the
plurality of flux barrier holes.
13. The motor according to claim 12, wherein the rotor cover is
made of a solidified fused material.
14. A motor comprising: a rotor portion rotating about a central
axis and including: a shaft arranged concentrically with the
central axis; a rotor core having a substantially cylindrical shape
attached to the shaft; and a plurality of field magnets arranged at
an outer circumferential surface of the rotor core facing the
central axis, and each of the plurality of field magnets extending
in a direction that is substantially parallel to the central axis;
wherein the rotor core includes: a plurality of magnet retaining
holes accommodating therein the plurality of field magnets; and a
plurality of flux barrier holes arranged in the direction that is
substantially parallel to the central axis at a space between a
corresponding pair of the plurality of field magnets, each
corresponding pair of the plurality of field magnets having a
magnetic polarity different from each adjacent pair of the
plurality of field magnets; wherein each of the plurality of flux
barrier holes is independent of a corresponding pair of the
plurality of magnet retaining holes; each of the plurality of
magnet retaining holes includes a concave portion extending toward
a corresponding flux barrier hole; and each of the plurality of
magnet retaining holes includes a gap clearance arranged to provide
a space between the field magnet accommodated therein, at a side
thereof circumferentially opposite from the concave portion.
15. The motor according to claim 14, wherein the corresponding flux
barrier hole is arranged radially outward from an imaginary line
that extends in a circumferential direction between adjacent
radially inward surfaces of the corresponding pair of the plurality
of field magnets; and there are no other magnets arranged between
the corresponding pair of the plurality of field magnets.
16. The motor according to claim 14, wherein the corresponding flux
barrier hole has a uniform shape in an axial direction.
17. The motor according to claim 14, wherein a magnetic pole
includes a pair of the plurality of field magnets between flux
barrier holes arranged circumferentially next to one another.
18. The motor according to claim 14, wherein a shortest distance
between each of the corresponding pair of the plurality of magnet
retaining holes and the corresponding flux barrier hole arranged
therebetween are equal to one another.
19. The motor according to claim 18, wherein the shortest distance
between each of the corresponding pair of the plurality of magnet
retaining holes and the corresponding flux barrier hole arranged
therebetween and a shortest distance between the corresponding flux
barrier hole and an edge of the rotor core are equal.
20. The motor according to claim 19, wherein the corresponding flux
barrier hole has a substantially triangular shape.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motor.
2. Description of the Related Art
In recent years, various components and mechanisms used in a motor
vehicle have been developed with specific focus on environmental
concerns (e.g., energy efficiency, reduction of carbon dioxide
emission, and the like). One of such mechanisms is an "idling stop"
mechanism which allows an engine of the vehicle not in motion to
stop automatically in order to reduce the carbon dioxide
emission.
However, when a compressor is activated by the engine of such
vehicle, each time the engine stops, the components activated by
the compressor, such as an air conditioner, also stop. In order to
prevent such inconvenience, the compressor of the components, such
as an air conditioner, is operated by a motor (e.g., IPM (Interior
Permanent Magnet)). That is, the compressor is activated by a car
battery, which allows the air conditioner or the like to continue
to operate even when the engine is not running.
However, a conventional IPM motor has a problem in that magnetic
flux leakage may likely to occur via the rotor core thereof at a
portion between permanent magnets of opposite magnetic polarity
which consequently decreases the efficiency of the motor.
Also, although durability of the rotor core of the IPM motor is a
critical issue since a great deal of centrifugal force is applied
thereto particularly at the portion in between the permanent
magnets, the conventional configuration of the IPM motor including
a hollow portion at the rotor core may not fully support such
force.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred
embodiments of the present invention provide a motor having a rotor
portion rotating about a central axis. The rotor portion includes a
shaft arranged concentrically with the central axis, a magnetic
rotor core having a substantially cylindrical shape arranged
attached to the shaft, a plurality of field magnets arranged at an
outer circumferential surface of the rotor core facing the central
axis, and each extending in a direction parallel or substantially
parallel to the central axis. The rotor core includes a plurality
of magnet retaining holes accommodating therein the field magnets,
and a plurality of flux barrier holes arranged in the direction
parallel or substantially parallel to the central axis at a space
between a pair of field magnets each having a magnetic polarity
that is different from one another. Each flux barrier hole is
arranged independently of a pair of magnet retaining holes each
accommodating therein the corresponding field magnet. Each magnet
retaining hole includes a concave portion extending toward the
corresponding flux barrier hole.
Also, a flux barrier hole may include a reinforcement portion
having a lower magnetic permeability than that of the rotor
core.
Other features, elements, steps, characteristics and advantages of
the present invention will become more apparent from the following
detailed description of the preferred embodiments thereof with
reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic plan view of a motor according to a first
preferred embodiment of the present invention.
FIG. 2 is a schematic longitudinal sectional view including a
central axis shown in FIG. 1.
FIG. 3 is a schematic plan view of a stator core of a stator.
FIG. 4 is a schematic perspective view of a plurality of wires
attached to the stator core of the stator.
FIG. 5A is a schematic plan view of a rotor core and a field
magnet.
FIG. 5B is a schematic diagram showing an enlarged view of the
rotor core surrounding a flux barrier hole.
FIG. 6 is a schematic longitudinal section view of a rotor portion
of a motor according to a second preferred embodiment of the
present invention.
FIG. 7 is a schematic cross sectional view showing a surface
perpendicular to the central axis of the rotor portion shown in
FIG. 6.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Note that in the description of preferred embodiments of the
present invention herein, words such as upper, lower, left, right,
upward, downward, top and bottom for describing positional
relationships between respective members and directions merely
indicate positional relationships and directions of the drawings.
Such words do not indicate positional relationships and directions
of the members mounted in an actual device. Also note that
reference numerals, figure numbers and supplementary descriptions
are shown below for assisting the reader in finding corresponding
components in the description of the preferred embodiments below to
facilitate the understanding of the present invention. It is
understood that these expressions in no way restrict the scope of
the present invention.
FIG. 1 is a schematic plan view of a motor 1 according to a first
preferred embodiment of the present invention. FIG. 2 is a
schematic longitudinal section view of the motor 1.
The motor 1 is a three phase motor which will be used as a
compressor for an air conditioner, or the like, in a motor vehicle
having an idling stop mechanism (that is, a mechanism for
automatically stopping an engine of the vehicle when not in
motion). As shown in FIGS. 1 and 2, the motor 1 preferably is
configured such that the central axis J1 is approximately twice as
long as a radial length.
As shown in FIG. 2, the motor 1 which is an inner rotor type
preferably includes a stator portion 2 which is a fixed assembly, a
rotor portion 3 which is a rotatable assembly, a bearing mechanism
4 which is arranged at the stator portion 2 and rotatably supports
the rotor portion 3 with respect to the stator portion 2 in a
concentric manner with the central axis J1, a resolver portion 5
which detects a rotational angle of the rotor portion 3 relative to
the stator portion 2, and a housing 6 which accommodates therein
the stator portion 2, the rotor portion 3, the bearing mechanism 4
and the resolver portion 5. The housing 6 preferably includes a
cylindrical portion for retaining the stator 21 (described below),
and a bottom portion for covering a lower side of the stator
21.
The stator portion 2 preferably includes the stator 21 arranged at
an inner circumferential surface of the housing 6. The stator 21
preferably includes a stator core 211 which is formed by laminating
a plurality of thin silicon steel plates on top of another. FIG. 3
is a schematic plan view of the stator core 211 according to the
present preferred embodiment. As shown in FIG. 3, the stator core
211 preferably includes a plurality (for example, 24 in the present
preferred embodiment) of teeth 2111 each extending outwardly in the
radial direction, and a core back portion 2112 having a
substantially annular shape arranged at an end portion of the teeth
away from the central axis J1.
FIG. 4 is a schematic perspective view of the stator core 211 and a
plurality (for example, 48 in the present preferred embodiment) of
wires 212 each attached to the stator core 211. As shown in FIG. 4,
each wire 212 preferably includes a portion which extends in a
parallel or substantially parallel manner with respect to the
central axis J1 at a slot 2113 which is defined between each two
adjacent teeth 2111 (i.e., in total, the stator core 211 preferably
includes 24 of slots 2113, for example).
The rotor portion 3 shown in FIG. 2 preferably includes a shaft 31
concentric with the central axis J1, a rotor core 32 having a
substantially cylindrical shape attached to a circumference of the
shaft 31 by a method such as pressing, a plurality of field magnets
33 each are thin plate of permanent magnet retained by the rotor
core 32, and a rotor cover 34 having a substantially discoid shape
arranged to cover both axial ends of the rotor core 32. The rotor
core 32 is formed by laminating a plurality of thin magnetic steel
plates in the axial direction. An outer circumferential surface of
the rotor core 32 is arranged opposite from an inner
circumferential surface of the teeth 2111 of the stator 21. Also,
the rotor cover 34 is made of a non-magnetic material (e.g., resin,
aluminum or the like). The rotor cover 34 is affixed to the rotor
core 32 by a bolt or the like. The rotor cover 34 minimizes axial
movement of the field magnet 33. According to the motor 1 of the
present preferred embodiment, the field magnets 33 are arranged
opposite from the stator 21 having an annular shape centered about
the central axis J1. When electric current is conducted to the
stator 21, a torque centered about the central axis J1 will be
generated between the stator 21 and the field magnet 33.
FIG. 5A is a schematic plan view of the rotor core 32 and the field
magnet 33. As shown in FIG. 5A, the rotor core 32 preferably
includes a plurality (for example, 16 in the present preferred
embodiment) of magnet retaining holes 321 arranged therethrough in
a direction parallel or substantially parallel to the central axis
J1. Each magnet retaining hole 321 has inserted therein the field
magnet 33. According to the present preferred embodiment, each
field magnet 33 inserted into the corresponding magnet retaining
hole 321 is divided into four sections in the axial direction. In
the description hereafter, each magnet retaining hole 321 which is
divided into four sections of the field magnets 33 will be referred
to as one field magnet 33.
As shown in FIG. 5A, a number of magnetic poles included in the
rotor portion 3 is preferably 8, for example. To be more specific,
a pair of field magnets 33 arranged next to one another form one
magnetic pole forming an approximately V-shaped configuration with
its opening facing away from the central axis J1.
The rotor core 32 of the present preferred embodiment preferably
includes a hole portion 323 arranged independently of the magnet
retaining hole 321 at a portion of the rotor core 32 between a pair
of field magnets 33 of opposite magnetic polarities arranged next
to one another. According to the present preferred embodiment, the
rotor core 32 preferably includes 8, for example, hole portions 323
each penetrating the rotor core 32 in a direction parallel or
substantially parallel with the central axis J1 which are arranged
in the circumferential direction evenly apart from one another and
relatively apart from the magnet retaining holes 321.
Since the rotor core 32 of the motor 1 includes the hole portion
323 at the portion arranged between the field magnets 33 of
opposite magnetic polarities next to one another, the magnetic
resistance at the portion 322 is increased. By virtue of such
configuration, leakage of magnetic flux at the space between the
field magnets 33 of opposite magnetic polarities next to one
another is minimized and thereby improving the motor efficiency.
That is, the portion at which the hole portion 323 is arranged
functions as a flux barrier. Hereinafter, such portion will be
referred to as a flux barrier portion 322 and the hole portion 323
will be referred to as a flux barrier hole 323.
FIG. 5B is a schematic diagram showing an enlarged view of a
portion of the rotor core 32 surrounding the flux barrier hole 323.
As shown in FIG. 5B, the flux barrier hole 323 is preferably
arranged at a portion at the flux barrier portion 322 defined by a
line 333 which is a line connecting a radially inward facing
surface of each field magnet of opposite magnetic polarities and a
radial end of the rotor core 32. Also, the flux barrier hole 323
whose cross section preferably has a substantially triangular shape
preferably penetrates the rotor core 32 in the axial direction.
The magnet retaining hole 321 preferably includes at a side thereof
nearer to the flux barrier hole 323 a gap clearance 324. The magnet
retaining hole 321 preferably includes at a side thereof facing the
flux barrier hole 323 a side portion 3211 which minimizes radial
and circumferential movement of the field magnet 33, and a concave
portion 3212 which extends toward the flux barrier hole 323. The
concave portion 3212 is preferably arranged between a pair of side
portions 3211. Note that a side portion 3211 arranged radially
outwardly of the concave portion 3212 will be referred to as an
outer side portion 3211a and one that is arranged radially inwardly
of the concave portion 3212 will be referred to as an inner side
portion 3211b. Also note that outer side portion 3211a and the
inner side portion 3211b each include a surface that is parallel or
substantially parallel with a surface of the flux barrier hole 323
which is parallel with the magnet retaining hole 321.
Also, the concave portion 3212 preferably includes an extended
concave portion 3212a which extends radially inwardly from the
concave portion 3212. By virtue of such configuration, the flux
barrier portion 322 is expanded so as to further minimize leakage
of magnetic flux, which improves the motor efficiency.
Also, the magnet retaining hole 321 preferably includes at an end
thereof opposite from the gap clearance 324 a gap clearance 325
(i.e., at an end thereof facing anther field magnet 33 of the same
magnet polarity). The gap clearance 325 is arranged such that the
gap clearance 325 and the inner side surface 3211b of the same
magnet retaining hole 321 are not parallel with one another.
Also, the gap clearance 325 preferably includes a portion which
makes contact with a portion of the field magnet 33. By virtue of
such configuration, radial and circumferential movement of the
field magnet 33 is minimized.
The substantially triangular shape of the cross section of the flux
barrier hole 323 preferably includes a side which extends in an
approximately parallel direction with the outer circumferential and
a pair of sides each extend in an approximately parallel manner
with the side surface 332 of the field magnet 33 facing the
corresponding flux barrier hole 323. Note that, as shown in FIG.
5B, D2 and D3 which are the shortest distances between the magnet
retaining hole 321 and the flux barrier hole 323 which are opposite
to one another are equal to one another.
The bearing mechanism 4 preferably includes, as shown in FIG. 2, an
upper bearing 41 and a lower bearing 42 which are attached
respectively at an upper portion and a lower portion of the rotor
core 32 to the shaft 31, and a bearing holder 43 which is affixed
to the housing 6 and in which the upper bearing 41 is accommodated.
The lower bearing 42 is accommodated in an accommodation portion
arranged at a bottom central portion of the housing 6 having a
substantially cylindrical side wall.
As described above, according to the rotor portion 3 of the motor 1
of the present preferred embodiment of the present invention, the
flux barrier hole 323 is arranged at the flux barrier portion 322
of the rotor core 32 so as to increase the magnetic resistance
thereof, and thereby minimizing leakage of magnetic flux at the
space between the field magnets 33 of the opposite magnetic
polarities next to one another and improving the efficiency of the
motor. Also, since the magnet retaining hole 321 includes the gap
clearance 324 extending toward the corresponding flux barrier hole
323, leakage of magnetic flux at the space between the field
magnets 33 of opposite magnetic polarities next to one another is
minimized further improving the efficiency of the motor.
According to the rotor portion 3 of the present preferred
embodiment, since the flux barrier hole 323 is arranged
independently of the corresponding pair of the magnet retaining
holes 321, durability of the rotor core 32 particularly near the
portion surrounding the flux barrier hole 323 is uncompromised.
Also, since the magnet retaining hole 321 includes the gap
clearance 324, the dimension of the flux barrier hole 323 is kept
at a minimum and therefore, durability of the flux barrier portion
322 is uncompromised. By virtue of such configuration, the flux
barrier portion 322 is operable to support the centrifugal force
applied to the field magnet 33 while the rotor portion 3 is in
motion improving the reliability of the motor 1.
Since a motor used as a compressor in an air conditioner or the
like in a motor vehicle or the like is expected to run efficiently
and reliably, the motor 1 according to the present preferred
embodiment of the present invention as described above in which
durability of the rotor core 32 is uncompromised and the efficiency
thereof is improved is particularly suitable for such use.
According to the rotor portion 3 of the present preferred
embodiment of the present invention, since each flux barrier hole
323 uniformly penetrates the rotor core 32 at the same cross
sectional portion thereof, magnetic resistance is evenly increased.
Therefore, the efficiency of the motor 1 is improved. Also, since
each magnet retaining hole 321 includes at the side thereof
opposite from the corresponding flux barrier hole 323 the gap
clearance 325, leakage of magnetic flux at a portion between two
field magnets 33 of the same magnetic polarity is effectively
minimized further improving the efficiency of the motor 1.
By virtue of such configuration of the rotor portion 3 in which a
pair of field magnets 33 arranged next to one another collectively
form a magnetic pole while each field magnet 33 is accommodated in
its own independent magnet retaining hole 321, the centrifugal
force applied to each field magnet 33 while the rotor portion 3 is
in motion is minimized and a load imposed on each flux barrier
portion 322 of the rotor core 32 is reduced. That is, the flux
barrier portion 322 is more durable against the centrifugal force
applied thereto which consequently increases relative durability of
the rotor core 32.
According to the rotor portion 3 of the present preferred
embodiment of the present invention, as shown in FIG. 5B, D1 which
is a distance between the flux barrier hole 323 and the outer
circumferential end of the rotor core 32, D2 and D3 which are
minimum distances between the flux barrier hole 323 and the
corresponding portion of the magnet retaining hole 321 are equal to
one another. By virtue of such configuration, an area of the flux
barrier hole 323 is maintained while reducing stress concentration
at the flux barrier portion 322 while the rotor portion 3 is in
motion, and therefore, durability of the rotor core 32 is improved
which improves the efficiency of the motor 1.
Hereinafter, a motor according to a second preferred embodiment of
the present invention will be described. FIG. 6 is a schematic
longitudinal sectional view of a rotor portion 3a of the motor
according to the second preferred embodiment. FIG. 7 is a schematic
cross sectional view showing a surface that is perpendicular or
substantially perpendicular to the central axis of the rotor
portion 3a.
As shown in FIGS. 6 and 7, the rotor portion 3a preferably includes
at each flux barrier hole 323, a reinforcement portion 341 made of
a material (i.e., preferably non magnetic material such as resin)
having a lower magnetic permeability than that of the rotor core
32. Note that in the description of the second preferred embodiment
of the present invention hereafter, elements similar to those
illustrated in FIGS. 1 through 5A are denoted by similar reference
numerals, and description thereof is omitted.
As shown in FIG. 6, the rotor portion 3a preferably includes a pair
of the rotor covers 34 which cover both axial ends of the field
magnets 33, and are made of the same material as the reinforcement
portion 341. Also, the rotor covers 34 are preferably made integral
with the reinforcement portion 341 by insert molding. By virtue of
such configuration, the flux barrier hole 323 is substantially
filled by a portion of the rotor cover 34.
As shown in FIG. 7, the rotor core 32 of the rotor portion 3a
preferably includes, as in the first preferred embodiment of the
present invention, at the flux barrier portion 322, the flux
barrier hole 323 independently of the magnet retaining hole 321.
Also, since the magnet retaining hole 321 includes the gap
clearance 324, the dimension of the flux barrier hole 323 is kept
at minimum and therefore, durability of the flux barrier portion
322 is uncompromised. By virtue of such configuration, leakage of
magnetic flux at the space between the field magnets 33 of opposite
magnetic polarities next to one another is minimized further
improving the efficiency of the motor.
According to the rotor portion 3a of the present preferred
embodiment of the present invention, since the flux barrier hole
323 includes the reinforcement portion 341, durability of the flux
barrier portion 322 is further improved. Also, since the plurality
of reinforcement portions 341 and the rotor covers 34 are
integrally formed, the manufacturing of the rotor portion 3a and
the motor is simplified.
While the present invention has been described in detail, the
forgoing description is in all aspects illustrative and not
restrictive. It is understood that numerous modifications and
variations can be devised without departing from the scope of the
invention.
For example, according to the motor of the second preferred
embodiment, the bolt may not be needed to affix the rotor cover 34
to the rotor core 32 if the rotor cover 34 is secured to the rotor
cover 34 via a plurality of reinforcement portions 341. Also, the
reinforcement portion 341 may be used as a balancer for the rotor
portion 3a.
Also, although the preferred embodiments of the present invention
described above assume that the cross section of the flux barrier
hole 323 preferably has a substantially triangular shape, the
present invention is not limited thereto. Also, although the
preferred embodiments assume that the rotor core 32 includes only
one flux barrier hole 323, the present invention is not limited
thereto.
Although the preferred embodiments of the present invention
described above assume that the flux barrier hole 323 penetrates
the rotor core 32, the present invention is not limited
thereto.
Although the preferred embodiments of the present invention
described above assume that the rotor portion includes a pair of
the field magnets 33 having the same magnetic polarity arranged
next to one another, the present invention is not limited thereto.
The rotor portion may include field magnets of opposite magnetic
polarities may be arranged next to one another. Also, the present
invention may include more than three of field magnets 33 of the
same magnetic polarity may be arranged next to one another.
Note that the field magnet 33 may be a thin plate having a curved
shape or a cylindrical shape extending in the axial direction.
Also, the present invention may be used as a power source for a
hybrid motor vehicle or the like.
While preferred embodiments of the present invention have been
described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing the scope and spirit of the present invention. The scope
of the present invention, therefore, is to be determined solely by
the following claims.
* * * * *